1. Field of the Invention
The present invention relates to a method of positioning a mask using a variable mask mechanism capable of controlling the amount of opening of an aperture for allowing an exposure light beam to pass therethrough when images on a negative film are exposed onto a photosensitive material and to a variable mask mechanism using the method, which is employed in, for example, a photographic printer or a printer-processor which is a combination of a photographic printer and a processor.
2. Description of the Related Art
A printer-processor is a so-called "mini-laboratory" and is used in a developing, printing and enlargement (DPE) shop or the like. In the printer-processor, a printer unit, which prints/exposes images recorded on a negative film onto photographic paper, and a processor unit, which effects development processing of the printed and exposed photographic paper, are combined into a single unit. By simply setting an elongated photographic paper at the printer-processor, the photographic paper can be automatically conveyed to the printer unit and the processor unit and processed thereat.
In the printer unit of the printer-processor, the images recorded on the negative film are enlarged to selected predetermined sizes and are printed onto photographic paper. The photographic paper on which the images of the negative film have been printed is successively conveyed to the processor unit where the negative film is subjected to developing processing so that the images are finished as photographic prints.
Panorama-size photographic prints whose transverse lengths are twice those of full size photographic prints, which is the normal size, have been widespread in addition to full-size photographic prints. Now, there is a tendency for image-frame sizes to increase.
Further, a frame-size switching camera is commercially available which can freely switch an aspect ratio between full-size frames corresponding to image frames of full-size and panorama-size frames corresponding to image frames of panorama size in the course of photographically recording a single negative film. When the frame-size switching camera is used, the single negative film is mixed with full-size image frames and screen-size image frames different in aspect ratio from full-size image frames such as panorama-size image frames, etc.
As a result, a drawback has become prominent particularly in recent years in that many types of negative masks for fixing negative films onto a negative carrier for positioning the negative films are required according to image frame sizes and a cumbersome process of replacing a negative mask with another is often needed. It has therefore been desirable to adopt a variable mask mechanism capable of changing the size of a negative mask without replacing the negative mask with another.
Even if this type of variable mask mechanism is adopted, it is necessary to measure the density of the negative film in advance when images on the negative film are printed onto photographic paper. Therefore, a light beam sent from the negative film side is transmitted to a density measuring unit located at a position different from the position of the photographic paper to measure the density of the negative film.
Thus, optical paths are different in length from each other when the density of each image is measured by the density measuring unit and the images are exposed onto photographic paper. In line with this, the degree of opening of the mask, which is originally required, is varied.
In the prior art, however, the mask is located in the same position so as to be able to meet conditions at the time of without varying the degree of opening of the mask between photometry and exposure. It is therefore necessary to more accurately position the mask than is required. As a result, the manufacturing costs of the variable mask mechanism is increased.